1. Field of the Invention
The present application relates to a motion sensing system, and more particularly to system of a motion sensing hand-held device having only two rotational sensors and a corresponding receiver device capable of generating rotational data around 3-axes based on output of the hand-held device.
2. Description of the Prior Art
When a motion-sensing pointing device is held by a user and pointed at a monitor, rotational axes are predefined as the Z axis pointing to the ground, the Y axis is in the direction from the pointing device to the monitor, and the X axis is at right angles to both the Z and the Y axes. In a system using a conventional pointing device, only the rotational outputs around the X and Z axes are needed for moving a cursor in the X′Y′ plane of the display screen. Therefore, when the conventional pointing device is used for pointing only, only two rotational outputs are needed.
Such a system is illustrated in U.S. Pat. No. 7,239,301, issued to Liberty et al., and herein incorporated by reference in its entirety. The patent discloses a conventional pointing device that includes an accelerometer that measures the acceleration it experiences and two rotation sensors for determining rotations around the X and Z axes. The rotational outputs are modified based on the acceleration determined by the accelerometer. The disclosed conventional pointing device provides rotational outputs around the X and Z axes only, and does not illustrate determining rotation around the third axis Y.
However, if a pointing device is to be integrated in a game system, the game system may need the rotational output around any one of the three axes (X, Y, Z), for playing a tennis or a golf game as examples, but the conventional pointing device cannot provide the third rotational output. Therefore, there is a need to provide a motion sensing system capable of determining the rotation around any of three axes without increasing the hardware cost.